PROJECT SUMMARY/ABSTRACT With widespread access to high-quality HIV treatment, awareness of HIV status remains among the most important barriers to public health control of HIV in sub-Saharan Africa, especially among key populations including adolescents, men, and close contacts of TB patients. Household testing by lay health workers offers a proven approach for reaching such populations, but rates of test acceptance remain unacceptably low. Stigma related to both HIV and TB contribute to low uptake, and may be reinforced by social interactions at the household level. A century of behavioral science research on individual decision-making in group contexts strongly suggests that optimizing the order of test invitations to establish testing as the normative choice, framing testing as a prosocial behavior, and offering a less invasive test is likely to reduce stigma and improve uptake of testing. Therefore, this application proposes a series of preliminary, prospective, mixed-methods studies with household members of TB patients and lay health workers delivering routine household contact investigation for TB and HIV in Kampala, Uganda. The overall objective of these studies will be to evaluate the feasibility, acceptability, and preliminary effectiveness of a complex behavioral intervention to reduce stigma and promote HIV testing uptake among household members of TB patients. The innovative testing strategy includes three components, 1) acceptance-optimized sequencing of test invitations, 2) prosocial messaging, and 3) oral HIV testing. In Aim 1, the novel test invitation strategy will be evaluated and iteratively refined based on serial qualitative data collection with health workers and household contacts, as well as before-and-after surveys of contacts using validated stigma scales selected for their utility for TB- and HIV-specific stigma at the household level. In Aim 2, the strategy will be prospectively evaluated for its effects on stigma and test uptake in a pre-post implementation design. A multi-disciplinary research team includes experts in case-finding for TB-HIV, social sciences, and implementation research working in close partnership with public health officials; they also have experience in building local research capacity in implementation science. The expected impact is to generate preliminary data on a novel approach to offering home testing that reduces layered HIV-TB stigma in households, and on its effects on testing and linkage to and retention in care, built on the strong scientific premise of longstanding research on social decision-making. The project will also enhance local capacity by supporting a local doctoral student on the project team and sponsoring annual scientific symposia on HIV-TB stigma at Makerere University, with the goal of engaging a broad group of stakeholders to advance a local research agenda in this area. These data will inform a future randomized study evaluating the clinical impact of these innovative stigma-reducing approaches to offering and delivering TB and HIV counseling and testing in household settings.